Meiosis is used in sexual reproduction to make genetically diverse gametes genetically diverse individuals

MEIOSIS

The production of eggs and sperm

The “Reduction Division ”

Mother Cell (2n) Gamete (1n)

Starts with 46 Ends with 23

Media Links\13_08Meiosis.mpg

Pre- Germ Cell OR Pre-Reproductive Cell

Mother Cell is diploid

2n = 46 BUT in this cartoon version ………

2n= 4

Interphase

Pre-Reproductive Cell#8 M.C. is 2n#10 Nucleolus

#2 duplication

Prophase I

Media Links\13-07b-ProphaseI.mov

#5 ds chromosomes

#9 N.M. gone

#12 Spindle Fibers

#13 Synapsis & Tetrads

#3 Crossing Over

Prophase I

Sister

Chromatids

Non-Sister

Chromatids

Synapsis - Homologous Pairs of chromosomes come together

Tetrad – 4 homologous chromatids

Media Links\13-10-CrossingOver.mov

Metaphase I

#6

Homologous pairs of chromosomes align on equator

Media Links\13-07c-MetaphaseI.mov

Anaphase I#7 Homologous pairs of chromosomes separate and are pulled to poles #11 ½ of homologous pair is at 1 pole, the other ½ is at the other pole

Media Links\13-07d-AnaphaseI.mov

Telophase I

#1

2 temporary daughter cells are 1n (ds)

Media Links\13-07e-TelophaseICytokin.mov

Cytokinesis occurs

Meiosis I Summary

1. Crossing Over Occurred

(Ensures Genetic Variation)

2. Separated the

Homologous Pair of Chromosomes

Cell went from 2N to 1N (ds)

3. Started as 2N = 46 (ds), ended as

N = 23 (ds)

Interkinesis – Meiosis Intermission

Are these cells 1N or 2N?

#1 Both cells are 1n (ds)

#6 Intermission of Meiosis

#8 Each daughter cell is genetically different

Prophase II

#1 1n (ds)

#5 ds chromosomes move to equator

#8 each daughter cell is genetically different

Metaphase II

#1 1n (ds)

#8 each daughter cell is genetically different

#9 chromosomes (ds) align on equator

Anaphase II

#2 Centromeres break

#7 (ss) chromosomes are pulled to poles

#4 (future) Daughter cells will be are 1n (ss)

#8 each daughter cell is genetically different

Telophase II

#3 Cytokinesis occurs

#4 Daughter cells are 1n (ss)

#8 Each daughter cell is genetically different

Media Links\13-07f-MeiosisIICytokin.mov

Gametes

#4

#8

#4 Daughter cells are 1n (ss)

#8 Each daughter cell is genetically different

Meiosis II Summary

1. Separated the chromatids,

Centromeres broke

2. 2 temporary daughter cells went from

Haploid (ds) to Haploid (ss)

3. Started as n = 23 (ds) ended as

n = 23 (ss)

Media Links\13_08Meiosis.mpg

And Now It Is Time To Start The Meiosis Lab...

Grab your Chromosomes Cups and begin!!!!!